McMahon was a well-known figure on the Central Coast, one who worked in many capacities for a number of local agencies and organizations. A Cal Poly graduate, she began her career as a reporter for the Paso Robles Country News and New Times. She entered the world of politics as a legislative assistant to former county supervisor David Blakely, and later Congresswoman Lois Capps. More recently, McMahon worked as an aide to Supervisor Jim Patterson when he was elected to the board, and later worked on the county supervisors advisory board.

McMahon was also a relentless environmental activist and a vocal supporter of a number of local causes, including the fight against development on the historic Santa Margarita Ranch. She also worked in the regional office of the Nature Conservancy and was the federal programs manager for the California Coastal Commission in San Francisco at the time of her death.

Patterson told New Times that one of McMahon’s legacies in SLO County was her sincere devotion to the preservation of agricultural land—and going about it by supporting the products of local agriculturalists.

“She wasn’t keen on developing on agricultural land, which a lot of people say you have to do,” Patterson said. “But what she did was work hard to market local agricultural products as a way to support local farmers and preserve our agricultural land. She recognized that to keep agricultural land we have to support local agriculture, and she understood that we have to spread the importance of local agriculture if we want to keep the rural landscape of San Luis Obispo. That’s what she breathed, and that’s what she lived.”

Patterson also said McMahon had been a personal friend of his for more than 30 years and he, as well as many others in the county, have a tremendous respect for what she accomplished in her life.

McMahon died peacefully at her Santa Margarita home surrounded by her family. She is survived by her husband and two sons.